extern vs MD

extern and MD both are nouns.

Word	Noun	Adjective	Verb	Adverb
extern	Yes	No	No	No
MD	Yes	No	No	No

As nouns, MD is a hypernym of extern; that is, MD is a word with a broader meaning than extern:

extern: a nonresident doctor or medical student; connected with a hospital but not living there
MD: a licensed medical practitioner

Other hypernyms of extern include doc, doctor, Dr., medico, physician.

extern (noun)	MD (noun)
a nonresident doctor or medical student; connected with a hospital but not living there	a doctor's degree in medicine
	a Mid-Atlantic state; one of the original 13 colonies, with capital Annapolis
	a licensed medical practitioner